Method and Apparatus for Sculpting Parabolic Shape

ABSTRACT

This invention is about a method and apparatus for fabricating large scale stationery parabolic solar collector. The method involves use of a robot like apparatus for sculpting shape of underlying base material to define contour of a parabolic collector. The reflective panels installed on the base material form a parabolic shaped mirror which reflects the sun&#39;s rays to a well defined focal point. The method of construction is scalable and can be used for fabricating small size parabolic collectors as well as large scale ones.

FIELD

This invention relates to solar heat collectors, more specifically tocomponents, parts and details of solar heat collectors. It is alsorelated to arrangements of mountings and supports of solar heatcollectors. The invention is also related to means for cleaning solarheat collectors. The invention is also related to mirrors with curvedsurfaces and more specifically to multifaceted mirrors.

BACKGROUND

Parabolic solar collectors are among the best known types of solarcollectors for concentrating solar radiation to a focal point. Paraboliccollectors are also used for concentrating electromagnetic rays to aspot and used onboard satellites as well as in ground stations forconcentrating radiation to a sensor. Database indicates there arenumerous patents related to parabolic collectors.

Literature survey indicated several documents that summarize state ofthe art in parabolic solar collectors. One of the documents is authoredby H. E. Imadojemu and published in Vol. 36, No. 4 issue in pages pp.225-237, 1995 of Energy Conversion Management Journal. This document istitled “Concentrating Parabolic Collectors: a Patent Survey”. Anotherarticle published is by S. Kalogirou and published in the Journal ofRecent Patents on Engineering in 2007, issue #1, pages 23-33. Thepublication by Kalogirou is titled as “Recent Patents in Solar EnergyCollectors and Applications”. The state of the art in solar collectorsis summarized in these articles.

Parabolic solar collectors are type of mirrors which have parabolicshape and installed facing towards sun. The solar rays coming from themirror are focused to a specific spot where an energy absorber or asecondary mirror is placed. These types of solar collectors are known as“SRTA” which stands for Stationary Reflector/Tracking Absorberconfiguration. In this particular configuration the solar concentratoris stationary, but due to changing position of sun, the point where thesolar radiation is focused changes continuously in a well-defined path.This is where the tracking absorber is used; by placing the absorberalways in the focal point of the solar collector, it is possible toreceive energy no matter what time of the day is.

The main problem with parabolic type SRTA's is the construction of theparabolic mirror. Although small size parabolic mirrors can be castefficiently using carefully designed molds, making oversized parabolicmirrors has been difficult and challenging. There have been patentstoward methods of making parabolic mirrors such as U.S. Pat. No.4,124,277 “Parabolic Mirror Construction” and U.S. Pat. No. 4,860,023,“Parabolic Reflector Antennas and Method of Making Same”. Another recentpatent application; US 2010/010-8057A1, “Inflatable Solar ConcentratorBaldwin Method and Apparatus” are among different attempts for makingparabolic solar collectors.

SUMMARY

The invention declares a method of making stationary parabolic concavemirror and an apparatus specifically designed for this purpose. Theprimary goal of this invention is to make large scale parabolic mirrorsquickly and accurately in an automated fashion by the aid of designedapparatus. One of the most difficult aspects of parabolic mirrorconstruction is formation of the specific parabolic shape accurately.The invention teaches a practical method of shaping underlying basestructure of the parabolic so that the mirror sheets placed over thesculpted base end up forming parabolic shaped mirror.

Another important problem addressed by this invention is the cleaningaspect of parabolic solar collector. Solar collectors require regularcleaning to keep the performance level high. Dust and dirt accumulateson reflective mirrors and degrades the reflective quality of the mirrorsurface. Unless the mirrors are cleaned regularly, the efficiency of thesolar collector gets reduced drastically. The cleaning approach used inmost contemporary solar collectors is manual cleaning using highpressure washers. If the mirror surface is large, the manual cleaningprocess can be very slow and tedious. The invention also teaches amethod of cleaning mirror surface in an automated way utilizing the sameapparatus used for construction of the parabolic structure.

The invention utilizes a robot like apparatus for construction of theparabolic mirror. The robot like apparatus has an end effecter which asuitable sculpting apparatus can be attached to suit the base materialthat needs to be shaped. During the construction phase differentsculpting tools are used as end effecters for shaping the underlyingbase structure. After the construction phase is over, the end effecteris attached with cleaning apparatus which can be used for automaticcleaning of the mirror face of the solar collector. Due to the automaticnature of cleaning process which requires no manual intervention, thecleaning can be performed during night time when solar collector is notutilized.

The construction apparatus of the parabolic mirror comprises a centralpost and a horizontal jib connected to the post which can rotate aroundthe central post. The horizontal jib has a trolley which can travelalong the length of the jib from center position to the tip. The trolleyhas a vertical working arm which is positioned perpendicularly withrespect to the trolley. The vertical arm mounted perpendicularly to thetrolley is free to move up or down under gravity or by external means. Abraking apparatus installed on the vertical working arm can stop thefree movement of the arm in case it is activated. The up or downmovement of the vertical working arm is further restrained by a systemof pulley and inelastic string which is strategically connected todifferent parts of the apparatus. The system of pulley and stringdetermines the tip position of the vertical arm as the trolley on thehorizontal jib moves back and forth. The arrangement is done such that,as the trolley moves along the jib, the tip of the vertical arm isforced to follow path of a perfect parabola.

The tip of the vertical arm is used for defining the contour of theparabolic mirror. By using appropriate attachments and continuouslyrotating the tip of the vertical arm around the central post, the basematerial underneath can be sculpted in parabolic shape. Just like alathe that shapes a metal piece by rotating and removing minisculepieces of the base material in each rotation, the jib and the verticalarm removes material from the base material underneath to sculptparabolic shape on the base material. By rotating the jib arm and movingthe trolley along the length of the jib arm, the tip of the vertical armcan be used to shape the sand, soil or material underneath the apparatusin parabolic shape. The tip of the vertical arm needs to be equippedwith appropriate tools for excavating or shaping the filler materialforming the base of the collector. The brake apparatus installed on thevertical working arm is used selectively during the carving phase of thebase material to limit the amount of material removed during theoperation. Just as a lathe is made to remove the base material graduallyin each turn, the brake mechanism used in the apparatus ensures onlymanageable amount is removed in each turn.

Base material can also be shaped by depositing additional material tothe base material. In a different embodiment of the invention, thesculpting apparatus is made to deposit material to the base materialrather than remove from it. By depositing varying amounts of fillermaterial by means of an appropriate applicator, the base is sculpted tohave parabolic shape.

Once the base material is shaped in the form of parabolic shape, thesurface of the base material can be covered by concrete, foam, adhesivematerial, metal mesh or any other agent to make the surface firm andsolid. The tip of the vertical arm can be equipped with appropriatedispensing tool to apply concrete, foam, adhesive material or any otheragent to the base material in a controlled manner so that dispensedmaterial conforms to parabolic shape.

The speed of the construction process can be increased by installingmore than one trolley on the horizontal jib. Each trolley has anindependent vertical working arm installed on it. The movement of thevertical arm is controlled by the string and pulley arrangementmentioned before. By fixing the focal point of each arrangement thesame, the tips of all vertical arms can be made to follow the sameparabolic path. By attaching appropriate tools to each one of the tips,the shaping or the cleaning process can be sped up.

Using the method and the apparatus declared in this invention, theparabolic shape construction can also be made partial rather than acomplete parabolic shape. This can be achieved by limiting the rotationangle of jib arm and the moving trolley within certain limits. This waya structure with partial parabolic shape can be constructed. Partialparabolic construction is valuable in case the physical space forconstruction is limited or the terrain is not suitable.

Using the method and the apparatus declared in this invention, theparabolic shape construction can also be tilted toward one side so thatfinal constructed parabolic surface can be used as offset-parabola. Theadvantages and proper use of offset-parabola is known to people whoknows this particular art. Partial offset-parabola construction can beachieved by placing central post at a tilted angle and restrictingrotation angle of the jib.

The parabolic shape can also be constructed on top of plastic, wood ormetal studs using the method and the apparatus described in thisinvention. In such cases, the tip of the vertical arm which defines aparabolic path which can be used for adjusting the length of the bracesor studs where the tips define a parabolic base for mirror.

When the construction process is over, the construction apparatus ismodified with different end effecter apparatus which will be used forcleaning purposes. Since mirror needs frequent cleaning to keepperformance level high, the vertical working arm of the apparatus isconverted to cleaning use by installing cleaning brushes on tip of thevertical arm. The pulley and string set up which is used to determinethe height of the piles is now used for determining the height of thebrushes that clean the parabolic mirror. By rotating the horizontal jibincrementally and moving the vertical trolley along the horizontal jib,the mirror can be cleaned mechanically by moving brushes or cleaningapparatus following contour of the mirror surface precisely.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the main parts of the parabolic mirror constructionapparatus,

FIG. 2 shows the construction process of the outer rim of the parabolicmirror,

FIG. 3 shows the details of the tip of the horizontal jib while restingon the outer rim,

FIG. 4A shows the basic principle of parabolic mirror,

FIG. 4B shows the working principle of construction apparatus,

FIG. 4C shows the general outlook of the pulley and string arrangementwith respect to the whole apparatus for determining the outlines of theparabolic shape,

FIG. 4D shows the details of the string and pulley arrangement and thevertical working arm set up,

FIG. 4E shows an alternative embodiment of the horizontal jib with morethan one trolley and vertical working arm which can be used for speedingup construction and cleaning process,

FIG. 5A shows the initial stage of process of shaping underlying basematerial,

FIG. 5B shows the interim stage of process of shaping underlying basematerial with brake assembly activated to inhibit movement of verticalworking arm,

FIG. 5C shows the final stage of process of shaping underlying basematerial,

FIG. 6 shows the block diagram of the elements that make up theapparatus,

FIG. 7 shows the flowchart of construction process,

FIG. 8 shows the flowchart of cleaning process.

DESCRIPTION

Now the method of operation and the details of the constructionapparatus will be described in detail with the aid of figures.

In the following text, the terms parabolic mirror, parabolic collectorall refer to the parabolic solar collector.

FIG. 1 shows the major parts that comprise the apparatus for makingparabolic mirror. The item labeled as 10 is the central post of theparabolic mirror. Item 20 is the horizontal jib which rotates aroundcentral post 10. Item labeled as 30 is the focal mast of the apparatus.Item labeled as 70 is the focal point of the parabolic mirror which isthe end point of the focal mast 30. Item 40 is the trolley which canmove along horizontal jib 20. Item 45 is the vertical working arm of thehorizontal jib. Item 50 defines the end point of the vertical workingarm 45. Item 60 is an inelastic string which is connected to point 70 onone side and to point 85 on the other side which is located on trolley40. While going from point 70 to point 85, the inelastic string goesover the roller at point 50 and makes a triangular shape. Item labeledas 80 is the end point of the horizontal jib 20 and it is equipped withrollers that rest on rim support 90. The rim support 90 is a platformraised on supports and partially carries the weight of horizontal jib20.

Central post 10 defines the geometric center of the parabolic solarcollector and the axis where the focal point of the parabolic solarcollector is located on. Since the focal point parabolic collector willbe determined by the central post 10, the location and the orientationof it is of crucial importance to the performance of the solarcollector. Declination angle of sun at a specific location on earth isvery much related to geographical latitude of that particular place. Ina preferred embodiment, the central post 10 should be slanted fromperpendicular position for the amount of declination angle to receivethe solar radiation in the most optimum manner. The determination ofdeclination angle is well known to the people who are skilled in thesolar collector art. By way of slanting the central post for the amountof declination angle, the parabolic collector constructed around thecentral post can be made to receive radiation of sun at or nearperpendicular angle for maximum duration of the day.

The steps of the construction process are now explained with the aid ofFIG. 2. As a first step, the central post 10 is placed in the groundwhere the parabolic mirror is to be constructed. As a second step thehorizontal jib 20 is attached to the central post 10 in such a way thathorizontal jib can rotate around the central post freely. The height ofcentral post 10 and the attachment point of horizontal jib 20 are highenough for the horizontal jib 20 to rotate around central post 10 in anunobstructed manner In a preferred embodiment the horizontal jib 20 isconstructed using triangulated lattice structure which makes thehorizontal jib lightweight yet mechanically strong.

The third step in the process parabolic mirror construction isconstruction of the rim support 90. In this particular step, thehorizontal jib 20 is fixed at the starting point of the rim and supportpile 101 is driven into ground right underneath the tip of thehorizontal jib 20. The height of the pile 101 is adjusted such that, theend point of the pile is at the same height with the end point ofhorizontal jib 20.

The process is repeated after horizontal jib 20 is rotated slightly andpile 102 is driven into the ground ending up at the same height as theend of jib 20. After driving more support piles into the ground andrepeating the process, rim runner platform 92 is installed on piles 100,101, 102 and 103. After completion of the process, rim runner platform92 will be supporting the end of horizontal jib 20 in the plane ofmovement of the horizontal jib 20.

FIG. 3 shows the detailed view of the horizontal jib 20 resting on rimsupport 90 with the aid of rollers 21 installed at the tip of thehorizontal jib 20. The rim support 90 defines the rim of the parabolicmirror and provides a support structure for the horizontal jib 20 torest and move on.

The fourth step of the construction method is explained by the aid ofFIG. 4 series. FIGS. 4A and 4B are used for explaining the basicoperational principle.

FIG. 4A shows cross section of a perfect parabolic mirror. X representsthe parabolic mirror with reflective face facing upwards toward sun.Rays A and B are coming from the sun which is situated directly overheadand parallel to axis MF of the parabolic mirror. F represents the focalpoint of the parabolic mirror. In a condition like this, the rays A andB will be reflected to point F of the mirror which is the focal point ofthe mirror X.

FIG. 4B shows a geometrical property of parabolic mirror. Assuming D isa line that crosses over parabolic mirror X, crossing line MFperpendicularly over center point of parabola designated as M, and C isa specific length line that is drawn perpendicularly to line D, thefollowing equations hold true:

distance GE+distance EF=K; where K is a constant,

as we move over line D.

The same formula is also valid for another instance,

distance HL+distance LF=K; where K is a constant,

In the drawing G and H are points where line C crosses line Dperpendicularly.

The apparatus makes use of this geometrical property to define outlineof the parabolic mirror which is further explained in FIG. 4C. Focalmast 30 is erected on top of the central post 10 in such a way that ashorizontal jib 20 turns around central post 10, the focal mast 30 alsoturns with the horizontal jib assembly. The end point of the focal mast30 is marked as 70 which define the focal point of the parabolic mirrorbeing constructed. Item 35 is a trolley that runs freely along thehorizontal jib 20 in the direction of 31-32. Item 40 is a verticalworking arm installed on trolley 35 which can move up or down freelyalong the direction 38-39 which is parallel to central post 10 andperpendicular to horizontal jib 20. The end point of the verticalworking arm 40 is designated as 50. An inelastic string 60 is connectedto focal point 70 on one end and passes over a roller placed at point 50and connected to point 46 on the other end. In this particulararrangement, as the trolley 35 moves along the horizontal jib 20 in thedirection of 31-32, the tip 50 of the vertical working arm 40 defines aparabolic path. Being inelastic, the length of string 60 remainsconstant but height of the vertical working arm 40 changes in accordanceto the principle explained in FIG. 4B. The focal point of the paraboladefined through this process is designated as 70. As the position oftrolley 35 and the rotational angle of horizontal jib 20 are changed,many points describing the outline of the parabolic profile areobtained.

The principle behind defining parabola is further explained as follows:Points 70, 50 and 46 in FIG. 4C define a triangle. In this triangle thefollowing geometrical relation exist due to inelastic nature of thestring:

-   -   (the distance from 70 to 50)+(the distance from 50 to        46)=constant    -   Vertical working arm 40 is perpendicular to horizontal jib 20        and can move up or down freely,

As a result of these constraints, the height of the point 50 which isthe end point of vertical working arm 40 varies as the trolley 35 ismoved on horizontal jib 20 from point 80 toward the center post 10.

The relationship between vertical working arm and inelastic string aswell as further details of the structure of trolley is explained withthe aid of FIG. 4D. Trolley 35 is installed on horizontal jib 20 and cantravel freely along the jib in the direction of 31-32. Vertical workingarm 40 has a roller attached at the end of vertical working arm which isdesignated as 50. Vertical working arm 40 is free to move in thedirection of 38-39. Inelastic string 60 which is connected to focalpoint on one end passes under the roller 50 and gets attached to thepoint 58 on the other end of the string. Point 58 is on trolley 35 andin close proximity to where vertical working arm 40 is connected totrolley 35. Item 95 indicates the sculpting apparatus connected to theend of vertical working arm 40. Item 99 indicates a brake assembly whichcan prevent movement of vertical working arm 40 in the direction of38-39 when activated.

A different embodiment of the horizontal jib arm is shown in FIG. 4Ewhere more than one trolley is installed on the horizontal jib arm.Horizontal jib 20 has two trolleys 35 and 36 installed on horizontal jib20. Each trolley 35, 36 have their own inelastic string 60 whichconnects the trolley to focal point 70 using the arrangement explainedin FIG. 4D.

FIGS. 5A, 5B and 5C explains the operation of the apparatus for shapingthe underlying structure. FIG. 5A shows initial state of the operationbefore the underlying base material is sculpted. In FIG. 5A the Item 72indicates the underlying base material which needs to be sculpted. Item35 is the vertical working arm with sculpting apparatus 95 attached tothe end. By rotating the horizontal jib 20 around central post 10 andmoving trolley 35 incrementally along the direction 38-39, the verticalworking arm 40 shapes the underlying base material 72 with sculptingapparatus 95. FIG. 5B indicates the interim stage of the fabricationprocess where the depth of the vertical working arm 40 is fixed by thebraking assembly 99 to enable removal of reasonable amount of basematerial 72 during the sculpting process by the sculpting apparatus 95.FIG. 5C indicates the final stage of the operation where the underlyingbase material 72 is sculpted in parabolic shape by sculpting apparatus95 after making repeated number of turns around central post 10 andrepeatedly moving trolley 35 along horizontal jib 20. Once theunderlying base structure is sculpted in parabolic form, the underlyingbase structure 72 is covered by mirror material to finish theconstruction of the parabolic mirror.

FIG. 6 shows the block diagram of the control system of the apparatuswhere the computer block 1 is interfaced to azimuth motor 2 whichrotates the horizontal jib along central post axis, trolley motor 3controlling position of the trolley travelling along horizontal jib,brake assembly 4 which inhibits movement of vertical working armselectively and sculpting apparatus control 5 which turns sculptingapparatus on or off selectively. Computer 1 also runs algorithm forconstruction and cleaning process.

The flowchart of the operation is illustrated in FIG. 7 which shows theflow chart of the operation during construction phase. The flowchartdescribes the steps for constructing the rim runner and sculpting of thebase material.

The rim construction process (90) starts by bringing the azimuth motorto starting position (91). Starting position is an arbitrary position,but once selected, it should be used as the starting position throughoutthe construction process. In this position the trolley is moved untilthe far end of the horizontal jib opposite to the central post (92). Atthis stage,the rim runner platform support piles are driven into theground and part of rim runner platform is placed on top of them (93).The height of the support piles should be as high as the tip of thehorizontal jib. After the pile driving process is over, azimuth motor isactivated and azimuth angle is increased for a predetermined amount(94). Horizontal jib is now pointing to a different support pilelocation. The process of driving support pile to ground is repeated forthis new position (93). The process is repeated over and over againuntil the starting position is reached again (95). At the end of thisprocess, the rim support piles are all driven into ground and the rimrunner platform is installed completely on these support piles. Now thetip of the horizontal jib can be supported by the rim runner platformunderneath.

The next process starts from the starting position of the horizontaljib. In the flowchart Y and X indicate distance of the trolley from thecenter. Y=100 means trolley is at the farthest point from the centralpost on the horizontal jib. The same notation is used for X, where X=100means farthest location from the central post. The trolley is moved tothe far end of the horizontal jib (96). The sculpting apparatus isturned on(98),and azimuth motor is started (99) to start the sculptingprocess. Horizontal jib makes a full turn while sculpting apparatus ison (100). This way, the outermost circumference of the parabolic shapeis constructed. The process is repeated by moving trolley closer tocenter gradually (79). While doing this, the vertical working arm isallowed to adjust its height for parabolic shape with brakes inde-activated state (81, 82). Once the trolley is in the new positionwith the vertical working arm height is adjusted to the new position,the brake assembly is activated and height of the vertical working armis fixed (83). Now the azimuth motor is turned on (84) and thehorizontal jib is allowed to make a full turn (85). After rotation iscompleted, the trolley is further moved closer to central post with theheight of vertical working arm is in fixed position (86). This processof turning azimuth motor and moving trolley closer is repeated untiltrolley reaches the center position (80). This process scrapes thesurface of the underlying base material and sculpts a surface with evenheight. (This is an intermediate stage of the process which is indicatedin FIG. 5B.) After this process, the trolley is moved into the previousposition which is indicated as process (79) in FIG. 7. While doing thisthe brake is deactivated (81) to adjust to the new height level (82)dictated by the parabolic shape and the process is repeated until theparabolic shape sculpting process is finished (88).

The cleaning process is also controlled by the computer system using thesame control system shown in FIG. 6.

FIG. 8 shows the flowchart of the cleaning process which essentiallymoves the motors in an organized way to clean the mirror. Before thecleaning process end effecter of the vertical working arm is equippedwith cleaning brushes. The cleaning process (70) starts by movingazimuth motor to the starting position (71). The starting position is anarbitrary position selected, but once selected, it should be maintainedas the starting position throughout the cleaning process. The trolley ismoved into the far end of the horizontal jib near the rim (72). Thecleaning brush motor is turned on (73) and azimuth motor is rotatedgradually (74) which causes the horizontal jib to rotate. Every timestarting position is reached the vertical trolley is pulled toward thecenter (76) and process is repeated. Eventually every part of the mirroris cleaned through this process. At the end of the cleaning process thetrolley is parked at a position near the central post and cleaningprocess is finished (78).

1. A method of manufacturing a parabolic solar collector, said methodcomprising: placing a central post into the ground, the central posthaving length, depth, and orientation in accordance with the desiredparabolic solar collector, attaching a horizontal jib to the centralpost, constructing a rim support under a tip of the horizontal jib,attaching at least one trolley that can move along the horizontal jib,attaching a vertical working arm to the trolley in a perpendicularposition that can move freely up or down on the trolley, restraining thevertical working arm with an inelastic string connected to a tip of thecentral post on a first end of the string and to the trolley on a secondend of the string while the vertical working arm rests on the inelasticstring by way of rollers, attaching a sculpting apparatus to the tip ofthe vertical working arm to shape an underlying base material underneaththe vertical arm, turning the horizontal jib incrementally around thecentral post in angular increments and shaping the underlying basematerial with the sculpting apparatus, moving the trolley along thehorizontal jib incrementally with distance increments and shaping theunderlying base material with the sculpting apparatus, placing a firmingagent on the shaped underlying base material, and placing at least onesheet with a mirror like surface on the shaped underlying base materialto form a parabolic shaped reflecting surface.
 2. The method of claim 1,wherein a tip of the central post defines a focal point of the parabolicmirror.
 3. The method of claim 1, wherein the horizontal jib turnsfreely around the central post and the rim support is placed under a tipof the horizontal jib.
 4. The method of claim 1, wherein the verticalworking arm moves freely up and down under gravity or by hydraulic,pneumatic, electrical means.
 5. The method of claim 1, wherein theinelastic string connected to the tip of the central post is only longenough to let the trolley reach the tip of the horizontal jib.
 6. Themethod of claim 1, wherein the sculpting apparatus to shape the basematerial comprises tool, dispenser, cutter, equipment operated bypneumatic, hydraulic, electrical means.
 7. The method of claim 1,further comprising selecting increments for turning and moving in such away that the sculpted underlying base material forms a parabolic shape.8. The method of claim 1, wherein the firming agent comprises concrete,metallic, chemical, biological material.
 9. The method of claim 1,wherein the said sheet with a mirror like surface comprises onecontinuous sheet forming a parabolic shaped reflecting surface.
 10. Themethod of claim 1, wherein said sheet with a mirror like surfacecomprises a plurality of sheets with mirror like surfaces arranged toform a parabolic reflecting surface.
 11. An apparatus for manufacturinga parabolic solar collector, said apparatus comprising: a central post,a horizontal jib, a set of one or more trolley travelling along thehorizontal jib, an inelastic string connected having a first endconnected to a tip of the central post and a second end connected to thetrolley, a vertical working arm placed perpendicularly on the trolley,the vertical working arm moving freely up or down and resting on theinelastic string, a sculpting apparatus placed at a tip of the verticalworking arm, a motor for incrementally turning the horizontal jib aroundthe central post, a motor for moving the trolley along the horizontaljib incrementally, a brake assembly to prevent the vertical working armfrom moving freely when activated, a set of one or more sheets withmirror like surface, a computer for controlling the movement of thetrolley, the horizontal jib, the vertical working arm,the brakeassembly, the sculpting apparatus and, a set of one or more brushes. 12.The apparatus of claim 11, wherein the horizontal jib is attached to thecentral post and rotated by the motor in such a way that the horizontaljib rotates around the central post under the control of the computer.13. The apparatus of claim 11, wherein the computer is configured tocontrol movement of the trolley by way of a motor along the horizontaljib.
 14. The apparatus of claim 11, wherein the inelastic string is longenough to let the trolley reach no further than an end of the horizontaljib.
 15. The apparatus of claim 11, wherein the vertical working armresting on the inelastic string is forced to move up or down as thetrolley travels along the horizontal jib as a result of changinggeometry of the inelastic string.
 16. The apparatus of claim 11, whereinthe sculpting apparatus attached to the vertical arm sculpts theunderlying base material underneath the vertical working arm by actionscomprising cutting, excavating, evaporating, sweeping, tamping,depositing.
 17. The apparatus of claim 16, where the sculpted underlyingbase material is covered by one or more sheets with mirror like surfaceforming reflective surface over the underlying base material.
 18. Theapparatus of claim 11 wherein the brake assembly prevents free movementof the vertical working arm under the control of the computer.
 19. Theapparatus of claim 11, wherein the set of brushes attached to thevertical working arm cleans mirror sheets underneath the verticalworking arm by actions comprising rotation, sweeping, polishing, rinsingand squirting.